Development of high-performance hydrogen storage alloys for applications in nickel-metal hydride batteries at ultra-low temperature

The main challenge for the applications of nickel-metal hydride (Ni-MH) batteries in low-temperature regions derives from the sluggish kinetics of its negative electrode materials-hydrogen storage alloys (HSAs). Here we design and fabricate a series of Co-free HSAs, exhibiting superior electrochemical reaction kinetics and low-temperature dischargeability performance. One novel candidate, La0.95Y0.05Ni4.5Mn0.4Al0.35, shows the highest discharge specific capacity of 283.5 mAh g(-1) among reported data of AB(5)-type HSAs at a high discharge current density of 3000 mA g(-1), which is 4.3 times that of the alloy synthesized with the same composition as a commercial alloy (MmNi(3.55)Co(0.75)Mn(0.4)Al(0.3)) electrode (65.9 mAh g(-1)). Moreover, this Co-free La0.95Y0.05Ni4.5Mn0.4Al0.35 alloy electrode can remain a discharge specific capacity of 255.8 mAh g(-1) at a low temperature of 233 K while the synthesized MmNi(3.55)Co(0.75)Mn(0.4)Al(0.3) alloy electrode shows a specific capacity of only 9.5 mAh g(-1). The discharge specific capacity of the above Co-free alloy electrode can reach 30.0 mAh g(-1) 228 K, making it a promising candidate as a negative electrode material for applications in Ni-MH batteries at ultra-low temperature.

Automated summary

A series of Co-free hydrogen storage alloys have been designed and fabricated, with La0.95Y0.05Ni4.5Mn0.4Al0.35 showing superior electrochemical kinetics and low-temperature discharge performance. This Co-free alloy electrode exhibits significantly higher discharge specific capacity compared to a commercial alloy electrode at high discharge current density, and maintains remarkable performance advantages at low temperatures.